Arrangement for automatically determining the weight of items of post

ABSTRACT

A device for automatically determining the weight of items of post comprising a feeding device (1) that contain conveyor belts that grip the postal items and conveys them in single file. A distributor (3) separates the incomming stream of items from the feeding device (1) into parallel conveying paths (TS) where they are weighed. The parallel conveying paths (TS) also contain belts which continue to grasp the postal items even as they are being weighed. Once the items are weighed, they are fed to a channelling device (4) which recombines the multiple streams of postal items from the parallel conveying paths (TS) into a single stream (2). The various conveyor belts in the various paths which grasp and convey the items of post are all run at the same speed as each other so that the original spacing between the postal items that was established while they were being conveyed by the feeding device (1) is retained while they are in the parallel paths (TS) so that the postal items can be recombined easily by the channelling device (4).

FIELD OF INVENTION

The present invention relates to an arrangement for the automaticdetermination of the weight of mail items.

BACKGROUND OF THE INVENTION

In automatic letter sorting systems, it is necessary for differentapplications to determine the weight of flat, flexible objects whichtear easily and which have different lengths, e.g., C6 letters, DLletters, C5 letters, postcards, these objects are transported as acontinuous stream, without stopping or delaying the objects.Difficulties can arise in that, the weight of the mail items must alsobe determined accurately and reliably when the mail items aretransported at high speeds, e.g., above a speed of 2 m/s. Even at thesespeeds, the mail items must not be damaged. In addition, it is necessarythat the mail items largely maintain their relative position withrespect to one another in the continuous stream. In particular, theweight determination should not change the gaps between the mail items.

Methods have already been disclosed wherein the objects to be weighedare guided horizontally over a weighing system and are weigheddynamically during this process. At higher speeds, however,displacements occur between the objects because the objects are notfirmly grasped by the conveying system; moreover, these arrangements donot allow high throughputs because, with small distances between theobjects the individual objects do not remain in the weighing system longenough to determine the weight with sufficient accuracy. If there areonly small gaps between objects of different lengths, the result is thatshort objects are not disposed in the weighing system by themselves, sothat, in these cases, it is not possible to determine the weight of thesmall objects at all. To solve this problem, the stream of objects canbe split into several partial streams and the individual objects fed toseveral weighing systems. In principle, this permits a higher overallthroughput. However, the problem continues to exist that the individualobjects of the partial streams can be displaced, so that sucharrangements cannot be used for higher speeds. Furthermore, there is therisk that the objects to be weighed get damaged during the transition tothe weighing system, especially if they are not rigid and stable enough.

BRIEF SUMMARY OF THE INVENTION

It is therefore the object of the present invention to propose anarrangement for the automatic determination of the weight of mail items.With such an arrangement a measurement can take place in the continuousstream while, even at higher speeds, displacements of the relativeposition of the mail items with respect to one another in the stream ofitems are avoided. The object is accomplished generally by anarrangement for the automatic determination of the weight of mail items,with a feeder arrangement and a discharge arrangement for the mail itemsas well as a plurality of weighing systems in which the feederarrangement is connected to a distributing device through which the mailitems can be supplied to the weighing systems. Further conveying pathsare provided through which the mail items can subsequently be suppliedto a combining arrangement and then to a discharge arangement. The mailitems are transported in the conveying paths and in the weighing systemswhile being permanently grasped. A plurality of conveying paths areconnected to the distributing device.

The arrangement according to the invention permits a higher overallthroughput of mail items while ensuring greater weighing accuracy andoperational reliability.

Advantageous embodiments of the invention can be taken from thedependent claims as well as from the descriptions [sic].

The invention is described below in greater detail by way of figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an arrangement according to the invention.

FIG. 2 is a detailed illustration of the conveyance through a weighingsystem according to the invention.

FIG. 3 is the layout for an arrangement according to the invention withtwo weighing systems.

FIG. 1 shows the block diagram of an arrangement according to theinvention. The mail items are fed to a conveying path TS having a feederarrangement 1, with the mail items being grasped permanently during theconveyance. This results in each individual item being fixed in itsposition in the conveying path TS with respect to the preceding and withrespect to the subsequent mail item. The feeder arrangement 1 isconnected via the conveying path TS preferably to a distributing device3. In this distributing device 3, the mail items are distributed to aplurality of conveying paths TS and fed to the weighing systems WS₁, WS₂. . . WS_(N). In these conveying paths TS, the mail items are alsopermanently grasped and transported. Within the weighing systems WS₁,WS₂ . . . WS_(N), the mail items are also permanently grasped andtransported and they are subsequently transferred to conveying paths TS'and are fed to a combining arrangement 4 via these conveying paths TS'.Then the mail items are fed to a discharge arrangement 2. Since the mailitems are permanently grasped and transported in the conveying paths andin the weighing systems, the relative distance of the mail items withrespect to one another in the stream of items is the same during thefeeding to the arrangement according to the invention as during thedischarge.

FIG. 2 shows that, according to the invention, the conveying paths andthe weighing systems are provided with twin band systems between whichthe mail items are clamped securely and are transported. Such a twinband system is comprised of two parallel extending belts which areguided over transport rollers and drive rollers 5-12. In all conveyingsystems TS, TS', mail items are transported to the weighing systems WS₁. . . WS_(N) with an identical predetermined speed, so that additionalacceleration or deceleration forces do not occur at the transitionpoints between conveying paths and weighing systems.

Preferably, each conveying path has a drive unit DU which is rigidlyconnected with a central drive D, e.g., a motor, so that the mail itemsare transported in all conveying paths, namely downstream as well asupstream of the weighing systems, with exactly the same speed, whilethis speed itself, however, is variable. The switching on and theswitching off of the drive D as well as a possible speed control iseffected by a control unit CU.

As was already mentioned, the mail items are transported in the weighingsystems with exactly the same speed, if possible, as in the conveyingpaths through which the mail items are fed or to which the mail itemsare fed, so as to prevent damage of the mail items. However, during thisprocess, a mechanical coupling between the conveying paths and theweighing systems must be avoided because, otherwise, the weighingsystems would not be able to determine the weight accurately. Accordingto the invention, therefore, each weighing system has a control unitCU₁, CU₂, . . . CU_(N), to which a signal as a measure for the speed ofthe conveying paths TS or TS' is supplied by a speed sensor SS.Furthermore, each system has one sensor SS₁, SS₂, . . . SS_(N), whichdetermines the local conveying speed in the weighing system. The signalof these local speed sensors SS₁, SS₂, . . . SS_(N) is supplied to thelocal control units CU₁, CU₂, . . . CU_(N), respectively. Furthermore,each weighing system has a local drive D₁, D₂, . . . D_(N) which iscontrolled by the control unit CU₁, CU₂, . . . CU_(N) to the speed ofthe conveying paths TS, TS'. This permits a transfer of the mail itemsfrom the conveying paths TS into the weighing systems or from theweighing systems into the conveying paths TS' without the appearance ofspeed differences, even if the arrangement must be switched off at anydesired moment during the operation.

The mode of operation of the arrangement according to the invention isas follows: mail items are supplied to the arrangement according to theinvention by the feeder arrangement 1, they first pass an input sensorIS, e.g., a light barrier, which records each mail item and relays it tothe control unit CU. The speed sensor SS determines the input speed ofthe mail items in the conveying path TS. This also permits the controlunit CU to track each mail item during its passage through thearrangement since the whereabouts of each mail item can be determined bymeans of integration as a function of the time. The mail items aresupplied to the distributing device 3 as a continuous stream and aredistributed to the weighing systems WS₁ to WS_(N). The individualweighing systems are mechanically decoupled from the remainder of thearrangement, so that their function is not impaired. The mail items aresupplied to the conveying paths TS' during the passage through theweighing systems and they are recombined to again form a continuousstream in the combining arrangement 4, which stream leaves thearrangement via the discharge arrangement 2.

FIG. 3 illustrates a preferred embodiment of the arrangement with twoweighing systems. Each weighing system WS₁ or WS₂ is disposed on a baseplate 13 or 14 which is mechanically decoupled from the remainder of thearrangement. Each weighing system is provided with a twin band system 15or 16 which transports the mail items while their weight is beingdetermined. The feeder arrangement 1 also has twin band systems. Aswitch is used as distributing device 3 to which the mail items aresupplied via a first or second conveying path 17 or 18, respectively.These conveying paths are also realized by twin band systems. Followingthe transport within the weighing systems, the mail items aretransferred to conveying paths 19, 20 which transport the mail items tothe combining arrangement 4. These conveying paths as well as thecombining arrangement are realized as twin band systems. The transferpoints between the conveying paths and the weighing systems arepreferably implemented by transport rollers which are offset withrespect to one another, so that, on the one hand, a reliable transfer ofthe mail items is permitted, on the other hand, the weighing system ismechanically decoupled from the remainder of the arrangement.

The weighing systems themselves each have the above-cited features,namely, a drive, a control device, a speed sensor as well as a conveyingpath in which the mail items are transported while they are permanentlygrasped. Furthermore, one of the different known weighing principles isused for the implementation of the actual weighing process in theweighing systems.

What is claimed is:
 1. An arrangement for the automatic determination ofthe weight of mail items, comprising:a high speed feeder arrangement; adistributing device connected to the feeder arrangement; a plurality ofconveying paths connected to the distributing device to supply mailitems to a respective plurality of weighing systems, with respectiveconveying paths and weighing systems having conveyors for gripping themail items; a plurality of additional conveying paths for supplying mailitems subsequently as output from the respective plurality of weighingsystems to a combining arrangement and then to a discharge arrangement,with respective additional conveying paths having respective conveyorsfor gripping the mail items; a respective driving arrangement providedfor each respective conveying path, with each respective drivingarrangement being rigidly connected to a central drive to be driven at asame, predetermined speed; and a respective controlled drive for eachweighing system causes mail items on the plurality of conveying pathsand in the respective plurality of weighing systems to be conveyed andpermanently gripped at the same, predetermined speed.
 2. The arrangementaccording to claim 1, wherein the plurality of conveying paths and theplurality of weighing systems support the weight of the mail itemsthrough the respective gripping conveyors.
 3. The arrangement accordingto claim 1, wherein the conveyors of the plurality of conveying paths,as well as of the respective plurality of weighing systems are providedas twin belt conveyor systems, between which the mail items are clampedand conveyed.
 4. The arrangement according to claim 3, wherein therespective twin belt conveyor systems solely support the weight of themail items.
 5. The arrangement according to claim 3, wherein the mailitems are conveyed in a horizontal direction by the twin belt conveyorsystems that are vertical relative to the conveying direction.
 6. Thearrangement according to claim 1, wherein a speed sensor is provided inthe region of the feeder arrangement and each weighing system has alocal speed sensor wherein the signals from the speed sensors are usedto control the drives of the respective weighing systems.